This invention relates to a method and apparatus for winding tape onto a cylindrical core to form a package of the tape and to a package of tape when built by the method.
Plastic tape for use in the manufacture of electrical cable and similar such uses has been manufactured for many years generally by slitting a wide band of the material into a number of separate tapes which are usually single ply and vary in commonly used width between 1/4" and 1/2" and in thickness between 5/10,000 TH of an inch and 20/10,000 TH of an inch. Tapes of this kind are slippery and difficult to handle in winding.
For many years tapes were wound onto a single spiral where one layer lies directly on top of the previous layer, and most wrapping machines from which the package of tape is used were built to accommodate only such single spiral tapes. In more recent years as automation and reduction of labour costs has become more important attempts have been made to form larger packages so as to reduce the labour content necessary to replace an empty package with a new full package on the wrapping machine.
In order to increase the amount of material in a package it is necessary to traverse the winding position axially of the cylindrical core on which the package is formed to form an elongate package much longer than the width of the material to be wound. In winding generally it is known to form either what is known as a parallel build package in which the material is laid helically with a small helix angle so that each turn of the material abutts the previous turn of material. It is also known to build what is known as cross wound packages where the helix angle is much greater than that required to traverse the winding position in the parallel build arrangement whereby the layers of material wound onto the package cross each other at an angle of the order of 20.degree.. Cross wound packages of tape have been manufactured successfully and have been sold for use with wrapping machines and other circumstances but because of the slippery character of the tape involved they have been prone to telescoping and collapse of the shoulders of the package. This has been a serious problem in the industry and has limited the size of packages particularly in relation to their diameter thus increasing the labour necessary to replace empty packages on the subsequent machines.
It is one object of the invention therefore to provide a method and apparatus for forming a novel structure of package from such tape, which package is more resistant to telescoping and collapse than previous packages.
The invention therefore provides according to a first aspect thereof a method of building a package of tape wound on a core comprising forwarding the tape from a supply thereof, guiding the tape to a winding position on the core, rotating the core to wrap the tape around the core and traversing the winding position across the core to form a package, characterized in that the winding position is intermittently traversed to visit repeatedly during the package build each in turn of a plurality of separate positions arranged axially of the core, and at each position is maintained stationary for a period of time to wrap tape spirally of the core.
According to a second aspect the invention provides an apparatus for building a package of tape wound on a core, comprising support means for the core, drive means for rotating the core to wrap tape therearound, guide means for guiding the tape on to the core at a winding position, and traverse means for reciprocating one of the guide means and support means relative to the other to traverse the winding position axially of the core to build a package, characterized in that there are provided traverse control means including means arranged to intermittently advance the traverse means such that the winding position visits each of a plurality of separate positions arranged axially of the core in turn repeatedly during the package build and means for halting the traverse means for a period of time such that the winding position remains at each said position in turn to wrap tape spirally of the core at the position.
According to a third aspect of the invention there is provided a package of tape when built by a method as defined above.
The invention therefore has the advantage that the package is formed substantially from a plurality of spirals arranged at the separate positions axially of the core with the spirals interconnected every few turns by a helical portion traversing from one spiral to the next. This forms a package which is more rigid in structure than previous packages and particularly the ends or shoulders of the package are formed mainly from a spiral and thus are stronger and more resistant to telescoping than conventional cross wound packages.
The positions are preferably spaced so that the separate spirals do not overlap but are separated only by a small extent to reduce the amount of traverse required to a minimum and to form a package of maximum density so as to contain the maximum material.
It is a further important feature of the invention that the traverse is maintained stationary at each position sufficient to wrap at least one full turn of material at that position so that each helical traverse is locked into the next adjacent spiral by a number of turns. The number of turns may lie between 1 and 5 depending upon the thickness of the tape but cannot be sufficient to form an appreciable step in the package since the tape will be prevented from overcoming the step when traversed in the opposite direction from the other end of the package.